Cylinder and piston arrangement



Allg. 5, 1958 L. LAUBENDER 2,845,917

CYLINDER ANDA PISTON ARRANGEMENT Filed Augf so, 1955 s sheets-sheet 2INVENTOR. L un we Mue/ips@ Allg 5, 1958 1 LAUBENDER I 2,845,917

CYLINDER AND `PIsToN ARRANGEMENT Filed Aug. so, 1955 s sheets-sheet s INVEN TOR Ludwig Laub :.nex

United States Patent O M CYLINDER AND PISTON ARRANGEMENT LudwigLaubender, Kassel, Germany, assignor to Firma Krauss-Malei A. G.,Munchen-Allach, Germany Application August 30, 1955, Serial No. 531,339

19 Claims. (Cl. 123-191) The present invention relates to a cylinder andpiston arrangement.

More particularly, the present invention relates to a cylinder andpiston arrangement which iinds particular use in internal combustionengines, especially of the diesel type.

There exist in the prior art cylinder and piston arrangements which areparticularly adapted for use in diesel type combustion engines,especially in two-cycle diesel engines. In View of the very hightemperatures to which the cylinders and pistons are subjected, provisionhas been made allowing for the expansion of such pistons. Pistons of theprior art therefore often include a tapered peripheral portion whichtapers toward the front end of the piston so that when the same expandsunder the influence of the operating temperature of a diesel engine,which is of the order of 700 C., the piston will assume a substantiallycylindrical shape.

These pistons are often formed with combustion chambers which open inthe front end faces of the pistons. Alternatively, a combustion chambermay be formed in the end wall or end face of a cylinder within which thepiston reciprocates. As is well known in the art, an explosive gaseousmixture is compressed 'between the end faces of the piston and cylinderso that when the piston is in its uppermost dead-center position withrespect to the cylinder, substantially all -of the gaseous mixture iscontained within the combustion chamber.

The cylinders and piston of the prior art are normally so constructedthat when these parts are at comparatively low temperatures, such asnormal room temperature, the end faces of the piston and the cylinderlie in planes normal to the piston axis. When the tapered end of thepiston is subjected to the operating temperature of the internalcombustion engine, this tapered end will assume a substantiallycylindrical shape, as set forth above, but at the same time the frontend face of the piston will curve so as to assume a convexconfiguration. The clearance between the front end face of the pistonand the end face of the cylinder within which it reciprocates is, in theuppermost dead-center position of the piston, of the -order of less thanl mm. If this clearance is reduced, the edge formed by -a combustionchamber within the piston and the front face thereof is extremely nearthe end face of the cylinder or if the combustion chamber is formed inthe cylinder, the edge formed by this combustion chamber and the endface of the cylinder is extremely near the end face of the piston. Ineither event, when the gaseous mixture within the combustion chamberexplodes, the increased pressure within the combustion chamber causesthe exploded mixture to flow through the space formed between the edgeand the end `face opposite the same at speeds which lie in thesupersonic range. Consequently, this edge becomes scaled, torn or mayotherwise be broken, damaged or weakened. As a result, the edge maybecome rounded or adopt any other undesirable configuration which will,y 2,845,917 Patented Aug. 5, 1958 2 prevent proper mixing of thegaseous mixture. Also, the mixing will then take place within anenlarged space and this inevitably results in high fuel consumption andinelticient engine operation.

It is therefore one of the objects of the present invention to overcomethe above disadvantages by providing a cylinder and piston arrangementmaking pos-sible very efficient operation of an internal combustionengine, particularly a two-cycle diesel type of internal combustionengine.

It is =another object of the present `invention to -provide a cylinderand piston arrangement wherein the piston, when exposed to the normaloperating temperatures of an internal combustion engine, will 'be ableto expand but will not reduce the clearance between the end faces of thepistonl and cylinder.

It is yet another object of the present invention to provide a cylinderand piston arrangement in which vone of these members is formed with acombustion ,Chamber opening in its end face wherein the piston, .whenexposed to the normal operating temperature of an internal combustionengine, will expand lbut will notreduce the clearance between the edgeof the combustion Chamber and the end face of the other member.

The objects Qf the present invention also include ,the provisionof apiston for use in `an internal combustion engine, which piston, whenexposed to the normal operating temperatures of the engine, will be ableto expand but will not reduce the clearance between-its end face and theend face of the cylinder within which it reciprocates.,

With the above objects in View, the present invention mainly consists in`that improvement in an internal combustion engine which comprises 4acylinder formed with an end face having a configuration substantiallyconstant at room temperature and at operating temperature vof theengine, and a piston ,slidably arranged in the cylinder and formed withan end face having such a conlguration at room temperature as toassumeanother contiguration at operating temperature lof the engine, whichother configuration `is substantially complementary to the substantiallyconstant configuration of the cylinder end face. According to thepresent invention, either the piston or the cylinder is formed with a:combustion chamber opening in the end face.

A piston according to a preferred embodimentof the present invention hasat room temperature a slightly dished front end face. The end face maybe a conicalconcave one having an angle of taper between O.5 and ,2.5"and preferably equal to approximately 11.5";- The piston may also have atapered peripheral edge portion adjacent and tapering toward the frontendface, the angle of taper of this edge portion being between 033 and1.0 and preferably equal lto approximately 0.5".

A cylinder and piston arrangement according to the present invention mayalso include ,a piston having at room temperature a flat front end faceand a cylinder having at roolrn temperature as well as at operatingtemperature of an internal combustion engine a slightly dished end face.

`The cylinder and face may be a conical-concave one hav- `ing an angleof taper between 0.5 and 2.5 and preferably equal to approximately 1.0so that when `the piston is exposed t0 the operating temperature of theengine the piston end face will bulge so as to assume a conical-convexconfiguration,substantially complementary to the conicalconcaveconliguratiQn 0f the Cylinder end face.

This application is a continuation-impart of my cepending applicationSerial No. 448,848, filed August 10, 195,4, now abandoned.

The novel features which are considered as characteristic forVtheinvention are set forth in particular in the 3' appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe fbest understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

Fig. 1 is a sectional view of a preferred embodiment of a pistonaccording to the present invention shown at a temperature below thenormal operating temperature of an internal combustion engine;

Fig. 2 is a sectional view of a cylinder and piston arrangement whichincludes the piston illustrated in Fig. 1, the parts being shown at thenormal operating temperature of an internal combustion engine;

Fig. 3 is a sectional view of another preferred embodiment of a pistonaccording to the lpresent invention shown .at a temperature below thenormal operating temperature of an internal combustion engine;

Fig. 4 is a sectional view of a cylinder and piston arrangement whichincludes the piston illustrated in Fig. 3, the parts being shown at thenormal operating temperature of an internal combustion engine;

Fig. 5 is a sectional view of another preferred embodiment of a cylinderand piston arrangement according to the present invention, the partsbeing shown below the normal operating temperature of an internalcombustion engine; and

Fig. 6 is a sectional view of the cylinder and piston arrangementillustrated in Fig. 5, the parts being shown at the normal operatingtemperature of an internal combustion engine.

Referring now to the drawings, and to Figs. 1 and 2 thereof inparticular, there is shown a piston 1 having a front end face 2. Thepiston is formed with a concavity 3 opening in the end face Z, whichconcavity forms a cornbustion chamber within which a gaseous mixture iscompressed during upward movement of the piston, as is well known in theart. The end face 2 is therefore an annular one, the concavity 3 forminga circular .edge 10 with the end face.

The concavity 3 is substantially concentric with the piston 1, but may,if desired, be slightly eccentric.

The piston 1 is shown in Fig. 1 while exposed to normal room temperaturewhich is very much below the normal operating temperature of a dieseltype internal combustion engine, which operating temperature is of theorder of 700 C. At such room temperature, the end face 2 is slightlydished so as to be frusto-conical or conical-concave and has an angle oftaper y formed between a plane tangent to the end face 2 and a planenormal to the axis of the piston 1. The angle 'y is between 0.5 and 2.5and is preferably equal to approximately 1.5

The upper portion of the piston 1, as viewed in Figs. l and 2, has atapered peripheral edge portion 7 which tapers toward the end face 2.This portion has an angle of taper formed between a plane tangent to thetapered peripheral edge portion 7 and the axis of the piston 1 or, as isshown in Fig. 1, a line or plane parallel to the The angle is between033 to 1.0, and is preferably equal to approximately 0.5". f

An angle a is formed at the upper edge 8 of the piston Iby theintersection of the frusto-conical end face 2 and the tapered peripheraledge portion 7, which angle is approximately equal to 90.

The piston 1 is slidably arranged for reciprocation within a cylinder,the end wall 6 and end face 5 thereof are shown in Fig. 2. In theinstant embodiment, the end face 5 lies in a plane substantially normalto the piston axis.

As set forth above, the piston 1 is illustrated in Fig. 1 while exposedto a temperature very much below the normal operating temperature of aninternal combustion chamber, as for example, a room temperature. Y Whenthe piston is exposed to the normal operating tempera# ture prevailingin the upper portion of the cylinder during operation of an internalcombustion engine, such as a twocycle Diesel type internal combustionengine, the piston will expand and assume the substantially cylindricalshape shown in Fig. 2. As a result, the end face 2 will deform upwardlyso that it lies in a plane normal to the piston axis, the angle aremaining substantially constant during the expansion of the upperportion of the piston. In practice, the angle a may, during expansion ofthe piston, increase very slightly inasmuch as the temperature in theimmediate vicinity of the end face 2 will be somewhat higher than in theimmediate vicinity of the edge portion 7 in view of the fact that thepiston rings (not shown) will conduct heat from the edge portion 7 tothe cylinder wall. It has been found that in an embodiment in which theangle 'y is equal to approximately 1.5 and the angle is equal toapproximately 0.5", so that the angle a is equal to approximately 89.0,the latter will upon expansion of the piston increase to approximatelyso that the piston will assume a substantially cylindrical shape.

At the top dead-center position of the piston a clearance 9 should bemaintained between the piston end face 2 and the cylinder end face 5,which clearance may be of the order of less than l mm.

Fig. 2 shows in `dotted line, the configuration assumed by a pistonhaving, at room temperature, a front end face normal to the axis of thepiston, when the end face of such a piston is exposed to the normaloperating temperatures of a Diesel engine. The front end face of such acylinder will bulge out so as to assume a convex configuration, as isshown by dotted line 11. As a result, the clearance 9 is materiallyreduced, especially in the vicinity of the edge 10, as is indicated at4, so that a gaseous mixture in the combustion chamber will, whenexploded, ow through the space 4 formed between the edge 10 and the endface 5. In practice, the speed at which the exploded mixture flowsthrough this space exceeds the speed of sound. As a result, the edge 10becomes scaled, torn and may otherwise be broken, damaged or weakened,so that the edge may become rounded or adopt any other undesirableconfiguration which would prevent proper mixing of the gaseous mixture.Also, inasmuch as the space within which the mixing takes place isenlarged beyond the volume within which the mixture is intended to bemixed, the engine will require a higher fuel consumption and willtherefore operate at a greatly decreased eliiciency.

The coniiguration of the cylinder end face will remain substantiallyconstant at room temperature as Well as at operating temperature of theengine, so that it will be understood that by providing a piston which,at such operating temperature, has a configuration complementary to thecylinder end face, the clearance between the piston and cylinder endfaces is not decreased below thc minimum clearance required for eicientengine operation.

In the embodiment illustrated in Figs. 1 and 2, the cylinder end face 2is normal 4to the piston axis so that a complementary piston end facewill likewise be normal to the piston axis. This is achieved byfashioning the piston so that its front end face will, at roomtemperature, be formed with a dish-shaped depression, as set forthabove.

While the dish-shaped depression of the piston end face 2 is, in Fig. l,shown as a frusto-conical one, any suitable slightly dishedconfiguration may be imparted to this end face.

Figs. 3 and 4 illustrate another preferred embodiment of the presentinvention and correspond t-o Figs. l and 2, respectively, in that Fig. 3shows a piston at a. temperature below the normal operating temperatureof an internal combustion engine and Fig. 4 shows the piston at normal-operating temperature. Piston l' of the instant ernbodiment differsfrom piston 1 of the above described embodiment in that no combustionchamber is provided within the piston 1. Instead, a combustion chamber 3is formed in the end lWall 6' of a cylinder within which the piston l'reciprocates. The combustion chamber 3 is substantially concentric withpiston 1', but may be slightly eccentric.

In all other respects, the instant embodiment is similar to the oneillustrated in Figs. l and 2.

When the piston 1 is exposed to the normal operating temperature of aninternal combustion engine, it will assume the configuration shown insolid lines in Fig. 4, whereas if the piston 1 were formed with an endface 2' lying, at room temperature, in a plane normal to the axis of thepiston, such end face would curve convexly, as shown by dotted line 11.According to the latter arrangement, the clearance between the edge 10',which edge is formed by the combustion chamber 3' and the end face andthe dotted line 11 would be materially decreased, as indicated at 4 inFig. 4. However, by fashioning the piston 1 with a slightly dished frontend face 2', the necessary clearance between the end face 2 and the edgelil at top dead-center position of the piston will be maintained at alltimes, even when the pist-on is subjected to the normal operatingtemperature of a Diesel engine.

While the dish-shaped depression in the end face 2 is shown in Fig. 3 asa frusto-conical one, any suitable .slightly dished configuration may beimparted to this end face.

Figs. 5 and 6 illustrate yet another preferred embodiment of the presentinvention and correspond to Figs. land 2, respectively, in that Fig. 5shows a cylinder and piston arrangement at a temperature below thenormal operating temperature of au internal combustion engine and Fig. 6shows the same arrangement at the normal roperating temperature of aninternal combustion engine. Piston 1 of the instant embodiment differsfrom the pistons of the above described embodiments in that the piston1" has an end face which, at room temperature, lies in a plane normal tothe piston axis. However, the end face 5 of the cylinder within whichthe piston 2" reciprocates is slightly dished so as to be frusto-conicalor conical-concave and has an angle of taper 'y" formed between a planetangent to the end face 5" and a plane normal to the common cylinder andpiston axis. The angle fy is between 0.5 and 25 and is preferably equalto approximately 1.0".

The cylinder end wall 6" is formed with a combustion chamber 3 which issubstantially concentric with the piston 1 but may be slightlyeccentric.

In all other respects, the instant embodiment is similar to theabove-described ones.

When the piston 1" is exposed to the normal operating temperature of aninternal combustion engine, it will assume the configuration sho-wn inFig. 6. This configuration is substantially complementary to theconfiguration of the cylinder end face S" so that a proper clearance 9will at all times be maintained between the end faces 2' and 5', theconfiguration of the cylinder end face 5" remaining substantiallyconstant at room temperature as well as at operating temperature of theengine. It is clear that if the cylinder end face 5 Were a iiat endface, shown in outline together with the combustion chamber by dottedline 11", the clearance between such a cylinder end face and the pistonend face 2. would be reduced, as shown at 4" in Fig. 6, below theminimum clearance required for elcient engine operation. However, byfashioning the cylinder and piston end faces so that the same arecomplementary to each other at normal operating temperature, therequired clearance 9" will at all times be maintained.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofcylinder and piston arrangements differing from the types describedabove.

While the invention has been illustrated and described `as embodied in acylinder and piston arrangement for use 6 in a diesel type internalcombustion engine, it is not-'intended to be limited to the detailsshown, since various modifications and structural changes may be madeWithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and `desired to be secured by Letters Patent is:

l. In an internal combustion engine, in combination, a cylinder formedwith an end face having a configuration substantially constant at roomtemperature and at operating temperature of said internal combustionengine; and a piston slidably arranged in said cylinder and formed withan end face having such a configuration at room temperature as to assumeanother configuration at operating temperature of said internalcombustion engine, said other configuration being substantiallycomplementary to said substantially constant configuration of saidcylinder end face.

2. In an internal combustion engine, in combination, a cylinder memberformed with an end face having a configuration substantially constant atroom temperature and at operating temperature of said internalcombustion engine; and a piston member slidably arranged in saidcylinder and formed with an end face having such a configuration at roomtemperature as to assume another configuration at operating temperatureof said internal cornbustion engine, said other configuration beingsubstantially complementary to said substantially constant configurationof said cylinder member end face, one of said members being formed witha combustion chamber opening in its end face. y

3. In an internal combustion engine, in combination, a cylinder memberformed With an end face having a configuration substantially constant atroom temperature and at operating temperature of said internalcombustion engine; and a piston member slidably arranged in saidcylinder and formed With an end face having such a configuration at roomtemperature as to assume another conguration at operating temperature ofsaid internal combustion engine, said other configuration beingsubstantially complementary to said substantially constant configurationof said cylinder member end face, one -of said members being formed witha combustion chamber opening in its end face, said combustion chamberbeing substantially concentric with said member. I

4. In an internal combustion engine, in combination, a cylinder formedwith an end face having a configuration substantially constant at roomtemperature and at operating temperature of said internal combustionengine; and a piston slidably arranged in said cylinder and formed withan end face having such a configuration at room temperature as to assumeanother configuration at operating temperature of said internalcombustion engine, said other configuration being substantiallycomplementary to said substantially constant configuration of saidcylinder end face, said piston being formed with a com bustion chamberopening in its end face.

5. In an internal combustion engine, in combination, a cylinder formedwith an end face having a configuration substantially constant at roomtemperature and at operating temperature of said internal combustionengine, said cylinder being formed with a combustion chamber opening inits end face; and a piston slidably arranged insaid cylinder and formedwith an end face having such a configuration at room temperature as toassume another configuration at operating temperature of said'internalcombustion engine, said other configuration being substantiallycomplementary to said substantially constant configuration of saidcylinder end face.

6. In an internal combustion engine, in combination, a cylinder formedwith an end face having a flat contiguration substantially constant atroom temperature and at operating temperature of said internalcombustion engine; and a piston slidably arranged in said cylinder andformed with an end face having a slightly dished configuration at roomtemperature and capable of assuming a fiat configuration at operatingtemperature of said internal combustion engine.

7. In an internal combustion engine, in combination, a cylinder formedWith an end face having a slightly dished configuration substantiallyconstant at room ternperature and at operating temperature of saidinternal combustion engine; and a piston slidably arranged in saidcylinder and formed with an end face having a flat conguration at roomtemperature and capable of assuming a slightly bulging configuration atoperating temperature of said internal combustion engine, said slightlybulging configuration of said piston end face being substantiallycomplementary to said slightly dished substantially constantconfiguration of said cylinder end face.

8. For use in an internal combustion engine having a cylinder ofpredetermined cross-sectional configuration provided with a top endsurface of a given configuration, a piston having a cross-sectionalconfiguration mating with that of the cylinder and having at roomtemperature, when the engine is not operating, a conical concave endface directed toward the top end surface of the cylinder, the angle oftaper of said end face being approximately 1.5 at room temperature whenthe engine is not operating, said end face of said piston changing, dueto expansion of said piston While the engine heats up to its operatingtemperature, to a configuration at the operating temperature of theengine which is substantially identical to the configuration of the topend surface of the cylinder at the operating temperature of the engine.

9. For use in an internal combustion engine having a cylinder ofpredetermined cross-sectional configuration provided with a top endsurface of a given configuration, a piston having a cross-sectionalconfiguration mating with that of the cylinder and having at roomtemperature, when the engine is not operating, a conical concave endface directed toward the top end surface of the cylinder, the angle oftaper of said end face being between 0.5 and 2.5 at room temperaturewhen the engine is not operating said end face of said piston changing,due to expansion of said piston While the engine heats up to itsoperating temperature, to a configuration at the operating temperatureof the engine which is substantially identical to the configuration ofthe top end surface of the cylinder at the operating temperature of theengine.

l0. For use in an internal combustion engine having a cylinder ofpredetermined cross-sectional configuration provided with a top endsurface of given configuration and side walls adjacent to said top endsurface of given configuration, a piston having a cross-sectionalconguration mating with that of the cylinder and having at roomternperature, when the engine is not operating, a slightly dished frontend face directed toward the top end surface of the cylinder as Well asa tapered peripheral edge portion adjacent and tapering toward saidfront face and directed toward said side walls of the cylinder, theangle of taper of said tapered peripheral edge portion beingapproximately 0.5 at room temperature when the lengine is not operating,said end face and said peripheral edge portion of said piston changing,due to expansion of said piston while the engine heats up to itsoperating temperature, to configurations at the operating temperature ofthe engine which respectively are substantially identical to thecongurations of the top encl surface and the side walls of the cylinderat the operating temperature of the engine.

1l. 'For use in an internal combustion engine having a cylinder ofpredetermined cross-sectional configuration provided with an innercylindrical surface and a top end surface of given lconfiguration at oneend of said cylindrical surface, a piston having a cross-sectionalconfiguration mating with that of the cylinder and having at roomtemperature a slightly dished front end face directed toward the top endsurface of the cylinder as well as a tapered peripheral edge portionadjacent and tapering toward said front face and directed toward saidcylindrical surface of the cylinder, the angle of taper of said taperedperipheral edge portion being between 0.33 and l.0 at room temperaturewhen the engine is not operating, said end face and said peripheral edgeportion of said piston changing, due to expansion of said piston Whilethe engine heats up to its operating temperature, to configurations atthe operating temperature of the engine which respectively aresubstantially identical to the configurations of the top end surface andthe cylindrical surface of the cylinder at the operating temperature ofthe engine.

12. For use in an internal combustion engine having a cylinder of apredetermined cross-sectional configuration provided with an innercylindrical surface and a top end surface of a given configuration atone end of said cylindrical surface, a piston having a cross-sectionalconfiguration mating With that of the cylinder and having at roomtemperature, when the engine is not operating, a conical concave endface directed toward the top end surface of the cylinder, the yangle oftaper of said end 4face being approximately 1.5 said piston also havinga tapered peripheral edge portion adjacent and tapering toward saidfront end face, and directed toward said cylindrical surface of thecylinder, the angle of taper of said tapered peripheral edge portionbeing lapproximately 0.5 at room temperature when the engine is notoperating, said end face and said peripheral edge portion of said pistonchanging, due to expansion of said piston While the engine heats up toits operating temperature, to configurations at the operatingtemperature of the engine which yrespectively are substantiallyidentical to the configurations of the top end surface and thecylindrical surface of the cylinder at the operating temperature of theengine. V

13. For use in an internal combustion engine having ya cylinder of apredetermined cross-sectional configuration provided with an innercylindrical surface and a top end surface of a given configuration atone end of said cylindrical surface, a piston having a cross-sectionalconfiguration mating with that of the cylinder and having at roomternperature, when the engine is not operating, a conical concave endface directed toward the top end surface of the cylinder, the angle oftaper of said end face being between 0.5 and 2.5", said piston alsohaving a tapered peripheral edge portion adjacent and tapering towardsaid front end face and directed toward said cylindrical surface of thecylinder, the angle of taper of said tapered peripheral edge portionbeing between 033 and 1.0 at room temperature when the engine is notoperating, said end face and said peripheral edge portion of said pistonchanging, due to expansion of said piston while the engine heats up toits operating temperature, to configurations at the operatingtemperature of the engine which respectively are substantially identicalto the configurations at the top end surface and the cylindrical surfaceof the cylinder at the operating temperature of the engine.

14. For use in an internal combustion engine having a cylinder ofpredetermined cross-sectional configuration provided with an innercylindrical surface and a top end surface of given configuration at oneend of said cylindrical surface, a piston having a cross-sectionalconfiguration mating with that of the cylinder and having at roomtemperature, when the engine is not operating, a conical concave endface directed toward the top end surface of the cylinder, the angle oftaper of said end face being between O.5 and 2.5", said piston alsohaving a tapered pe- -ripheral edge portion adjacent and tapering towardsaid front end face and extended toward said cylindrical surface of thecylinder, the angle of taper of said tapered peripheral edge portionbeing between 0.33 and 1.0 at room temperature when the engine is notoperating, said end face and said peripheral edge portion of said pistonchanging, due to expansion of said piston while the engine heats up toits operating temperature, to configurations at the operatingtemperature of the engine which respectively are substantially identicalto the configurations of the top end surface and the cylindrical surfaceof the cylinder at the operating temperature of the engine, said pistonbeing formed with a combustion chamber opening in said end face.

15. In an internal combustion chamber, in combination, a cylinder havinga conical concave end face substantially constant at room temperatureand at operating temperature of said internal combustion chamber, theangle of taper of said end face being approximately 1.0; and a pistonslidably arranged in said cylinder and formed with an end face having aflat configuration at room temperature and capable of assuming aslightly bulging coniiguration at operating temperature of said internalcombustion engine, said slightly bulging configuration of said pistonend face being substantially complementary to said conical concavecylinder end face.

16. In an internal combustion chamber, in combination, a cylinder havinga conical concave end face substantially constant at room temperatureand at operating temperature of -said internal combustion chamber, theangle of taper of said end face being between 0.5 and 2.5 and a pistonslidably arranged in said cylinder and formed with an end face having aflat configuration at room temperature and capable of assuming aslightly bulging configura- Ition at operating temperature of saidinternal combustion engine, said slightly bulging configuration of saidpiston end face being substantially complementary to said conicalconcave cylinder end face.

17. In an internal combustion engine, in combination, a cylinder formedwith an end face having a slightly dished configuration substantiallyconstant at room temperature and at operating temperature of saidinternal combustion engine, said cylinder being also formed with acombustion chamber opening in its end face; and a piston slidablyarranged in said cylinder and formed with an end face having a atconfiguration at room temperature and capablo of assuming a slightlybulging configuration at operating temperature of said internalcombustion engine, said slightly bulging configuration of said pistonend face being substantially complementary to said slightly dishedsubstantially constant configuration of said cylinder end face.

18. In an internal combustion chamber, in combination, a cylinder havinga conical concave end face substantially constant at room temperatureand .at operating temperature of said internal combustion chamber, theangle of taper of said end face being approximately 1.0", said cylinder-being also formed with a combustion chamber opening in its end face;and a piston slidably arranged in said cylinder and formed with an endface having a flat configuration at room temperature and capable ofassuming a slightly bulging configuration at operating temperature ofsaid internal combustion engine, said slightly bulging configuration ofsaid piston end face being substantially complementary to said conicalconcave cylinder end face.

19. In an internal combustion chamber, in combination, a cylinder havinga conical concave end face substantially constant at room temperatureand at operating temperature of said internal combustion chamber, theangle of taper of said end face being between 0.5 and 2.5, said cylinderbeing also formed with a combustion chamber opening in its end face; anda piston slidably ar- [ranged in said cylinder and formed with an endface having a Hat configuration at room temperature and capable ofassuming a slightly bulging configuration at operating temperature ofsaid internal combustion engine, said slightly bulging configuration ofsaid piston end face being substantially complementary to said conicalconcave cylinder end face.

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